A sedative long used by physicians and dentists, nitrous oxide – popularly known as “laughing gas,” is being increasingly consumed as a party drug. Among its common effects are a feeling of relaxation, euphoria, lightheadedness and occasionally mild hallucinations. Recreational users typically inhale the odourless, colourless gas from party balloons filled by freely sold nitrous oxide cartridges. It acts almost immediately, the effects lasting from several seconds to three minutes, says Andrea Piest, a specialist for Berlin’s emergency drug and alcohol addiction service. Laughing gas can be da…